Science Fair Idea: Re-orienting Your Globe

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Fifty years ago this month, the March 1972 issue of Elementary Electronics showed this idea to improve the utility of the globe in your radio room. Normally, the globe is mounted so that it spins just like the Earth–along its axis. But you’re not required to spin the globe, and it becomes more useful if you orient it so that it can turn along an axis through your location and your antipode–the point furthest away from you.  If you’re in North America, that would be somewhere in the Indian Ocean.

The advantage of doing this is that it quickly lets you see the direction and distance to any other point.  The thing holding the globe in place (known as the semi-meridian) is usually marked in degrees.  But you can tape a scale in miles to it, and if you rotate any point on the globe toward that line, you’ll instantly see the number of miles.

All you need to do is remove the globe from its mounting, which is usually just a matter of slipping it out.  You then drill a new hole at your location and at the opposite side, and remount it.

The student desiring to bring home the blue ribbon at the science fair will quickly realize that this simple project will answer the question of “how to convert a globe into a distance measuring instrument.”



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Dan Gibson Parabolic Microphone

1072MarPMShown here is Canadian wildlife photographer Dan Gibson using the parabolic microphone he developed. Here, he has the mike mounted on the prow of his canoe, which allows him to silently paddle up in search of wildlife.

This photo is from the March 1972 issue of Popular Mechanics, in which he is described as a photographer who developed the tool primarily to capture photographs of wildlife. The article hinted, however, that the system could be used to capture wildlife sounds on tape. Thanks to this microphone, Gibson became more famous as a recording artist, with his Solitudes series of recordings of nature sounds and music. Here, for example, is his recording of La Mer (Beyond the Sea):

You can find the label’s recordings on Amazon, or find more information at their facebook page. If you’re looking for a parabolic microphone, here are some of the current offerings:



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Radio Repairmen: Carrying the Whole Load

1942MarServEighty years ago, the radio servicemen of America were rolling up their sleeves, because as of April 22, 1942, as we’ve previously reported, they would carry the whole load of making sure Americans had access to the vital information and entertainment provided by their radios. Just as before, they would have to keep doing minor repairs. But in the past, there had been some sets that were so far gone that they would just be thrown away and replaced.

But the last new radio would roll off the assembly lines on April 22, so throwing away an old set was no longer an option. Many of the sets needing repairs would be older, so this ad encouraged dealers to order a full set of Rider manuals, which consisted of schematics and service data for virtually every radio built in the USA.

The ad appeared in the March 1942 issue of Service magazine.



1952 Radio-Intercom

1952MarPM11952MarPM2Traditionally, the March issue of Popular Mechanics carried a radio project dubbed the “Little Giant,” a project aimed at advancing students who could make something serving a useful purpose. The March 1952 issue carried on the tradition with the set shown here. It was the customary five-tube superheterodyne, but it also included an intercom.

The magazine noted that a good radio combined with an intercom was an instrument of pleasure as well as utility. It could allow you to listen to the radio in two places, or it could be used as a monitor to send programs to or listen in to the kids in the nursery.

All of the controls were on the master station. The remote consisted of just a speaker, which also doubled as the microphone.

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1942 Blackout Advice

1942MarPSEighty years ago this month, the March 1942 issue of Popular Science carried a number of pointers on preparing for wartime blackouts. The magazine first noted that deciding whether or not to participate wasn’t a merely personal decision: If you didn’t follow the blackout instructions, then both you and your neighbors would be put at risk.

The good news was that it was very unlikely that large sections of the country would be subject to blackout. Therefore, it advised against running out and buying the necessary materials: You might wind up with a bunch of stuff that you don’t need, and even worse, you could cause shortages in areas where they were needed. So the key advice was to wait for official advice from civil defense authorities, and follow their instructions. In the meantime, you could read up to be prepared for that time, such as with the hints shown above. In addition, the magazine contained numerous ideas for blacking out various kinds of windows and doors. One key piece of advice was to remove bulbs from unused sockets, especially outdoors. No matter how well you were blacked out, an accidentally flipped light switch could make it all for naught for you and your neighbors.

When civil defense authorities gave you the instructions to prepare for blackout, you would be ready.



1942 Two Tube Regen

1942MarRadioCraftEighty years ago this month, the March 1942 issue of Radio Craft carried the plans for this two-tube shortwave regenerative receiver. Thanks to the use of dual 1JG6 triodes, the set had four-tube performance. One half of the first tube was an untuned amplifier, which prevented the regenerative detector from radiating and messing with other sets in the neighborhood. The regeneration was controlled with a variable capacitor, and the second tube provided two stages of audio amplification.

With four plug-in coils, the set covered 145 through 10 meters. The compact size made the set ideal for portable operation.

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Tree Antenna, 1962

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1962MarEI1Sixty years ago this month, the March 1962 issue of Electronics Illustrated carried these self-explanatory plans for the stealth antenna shown at left. It was billed as a way to fight TV interference, basically by keeping a low profile and thus not alerting potentially suggestive neighbors to the possibility that their picture was other than perfect.

And for the patient ham, the illustration above demonstrates a method of adding multiband capability.

The article was penned by prolific writer Howard Pyle, W7OE.



12 Volt Power in 6 Volt Car, 1952

1947MarQSTFinding the right power supply for a particular piece of equipment has always been an issue, as shown by this Hints and Kinks item from the March 1952 issue of QST.  There was a lot of surplus gear on the market, much of which ran on 12 volts. Most vehicles, on the other hand, had 6 volt systems. Kermit Karns, W0MYH, of Kansas City, had a 1948 Chevrolet with a 6 volt power system and submitted his solution for running 12 volt equipment in his car.

He simply added another generator and another battery to the car, essentially giving him two independent 6 volt systems, and one 12 Volt system for his radio gear. An additional 6 volt generator, identical to the one that came with the car, was mounted under the hood, and the second battery was stowed away under the driver’s seat. One of the two regulators in the diagram was for a positive ground vehicle, and the other was for a negative ground system.

In addition to being able to run his radio equipment in the vehicle, the added advantage was that the car now had two electrical systems. Karns noted that one was used primarily for the starter with the other loads attached to the second system.



1962 Clown Radio


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1939JanPSWe previously showed you a radio at left that was sure to delight the youngsters of 1939.  It featured a creepy face with eyes that lit up in time with the music.

Not to be outdone 23 years later, the publishers of Popular Mechanics published in the March 1962 issue the plans for the same general idea shown here. This time, the face, a clown, was a little bit less creepy, but it still had magic eye tubes in the place of eyeballs, and the eyes flashed in time with the music. The magazine gave two options for the project. If you didn’t have a radio to spare, then you could build the entire radio, which was basically a crystal set using 1N34 diode, with two tubes to provide loudspeaker volume. The magazine noted that this worked satisfactorily in downtown Chicago, and pulled in three different stations with a 50 foot antenna on the roof. According to the magazine, this simple circuit was “the minimum performance which might satisfy youngsters.”

But for better performance, it was recommended to just use an existing radio, and tap in the additional circuit, shown below, to flash the eyes. The magazine showed a template for cutting the clown face, but also noted that the prepunched chassis and clown face were available from the Experimenter’s Supply Co., 1924 W. Columbia Avenue, Chicago.

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1922 AM Transmitter

1922MarPM1A hundred years ago this month, the March 1922 issue of Popular Mechanics carried the full construction details for this AM transmitter for the radio amateur. Heretofore, constructing such a transmitter was an expensive proposition, since it invariably required a motor-generator to provide the high voltage. This transmitter, however, used a “new type of transformer” to supply the 500 volts of B+ from household current, “as simply as screwing in a lighting bulb or plugging in an electric iron.” Two rectifier tubes could be of “any of the various types on the market,” and the transmitter itself used three UV-202 tubes.

The price of all of the parts was said to be about $125. According to this inflation calculator, that works out to over $2000 in 2022 dollars, so this was not the project for the impecunious.

The article noted that the exact range would, of course, vary with local conditions. But the author reported that music and voice had been transmitted from 100 to 200 miles, and under especially good conditions, an extreme range of 500 miles had been recorded.

The author, whose later call sign was W9DCX, went on to become the magazine’s radio editor. He died in 1955, as noted in his obituary in the magazine.

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